Beefed-up police presence for the London Marathon on April 21 will remain in place despite the death and capture of the Boston Marathon bombing suspects. / Leon Neal, AFP/Getty

by Kim Hjelmgaard, USA TODAY

by Kim Hjelmgaard, USA TODAY

LONDON -- Less than a week after bombs exploded at the finish line of the Boston Marathon, those taking part at the London Marathon were refusing to let fear cast a shadow over Sunday's race.

On a chilly, but entirely clear, spring morning in the Blackheath area of the capital city's south-east corridor, thousands of runners and their supporters observed a 30-second silence in a show of respect to the three people killed and more than 170 injured during last Monday's traumatic events and the fraught aftermath.

But Sunday, many in the assembled crowd made clear, was not a day to be cowed or to give in. There may not have been the marked sense of jubilation or as much giddy, nervous energy as can sometimes accompany these events, but many runners were determined to make the best of it.

"We have confidence in London," said Nicola Selwood, who was waiting for the mass start. "We put on the Olympics, so we can do this." Selwood said that the city, and this race, should not be put off by terrorism.

But standing alongside Selwood was Clare Shepherd. "I just want to get around the course safely," she said. And Graham Law, another runner, added, "If there's worry, it's more for our families who are watching today."

Damian Crosby, a banker from London who was running Sunday, said his family would be out supporting him "so obviously their security is in the back of my mind.

"But you just need to get on with it. That's the British way."

London Marathon runners have raised more than $900 million in memory of a deceased loved one or to support a charity since the event was unveiled in 1981. Sunday, there was another reason to take part: Many ran in honor of those killed or injured in Boston.

London is showing its solidarity with the people of the Commonwealth - the Massachusetts one - in a number of ways.

A Twitter campaign launched by Lucy-Fraser Macnamar, otherwise known as @DayCentreLucy, was encouraging runners to "place your hands over your hearts as you cross the finish line in tribute to #Boston #handsoverhearts."

Race officials said they did not have any way of tracking how many runners who competed in Boston also took part in the London Marathon.

The organizers of the London Marathon have pledged to donate about $5 for every finisher to The One Fund Boston, set up by Massachusetts Gov. Deval Patrick and Boston Mayor Thomas Menino to help those most affected by what occurred in Boston.

But as more than 35,000 runners and half a million spectators descended on the marathon's 26.2 mile route that snakes through the streets of the capital - from Blackheath in the southeast, to the Mall near St James' Park, north of the River Thames - Monday's explosions have caused London to rethink security arrangements.

London's Metropolitan police said police numbers would be boosted by 40% compared with last year, with several hundred additional officers on the streets providing "visible reassurance to the participants and spectators alike."

As a further security precaution, trash cans along the marathon's course were removed.

"I would stress there is no change to the threat level to London and nothing at this stage to link the Boston bombings to the London marathon," said Chief Supt. Julia Pendry, the Met's ranking officer in charge of security at Sunday's race.

"Nevertheless we want to do all we can to help provide a secure environment in which the runners, spectators and volunteers can enjoy themselves," she said.

A mounted bike officer from London's Metropolitan police who was guarding thousands of personal items, some of which from a distance resembled bags, said that so far everything was going to plan. The officer, who was not authorized to speak to the news media, did not express concern that the bags that runners had left behind on the lawns at Blackheath posed a security risk.

Londoners know something about terrorism, having lived through the deadly "7/7" public transit bombings of 2005 and numerous attacks by Northern Irish terrorists, and were glad to show their solidarity with Boston.

"We've had this in London, and it's nice to send the message that life goes on and that we can still do everyday, ordinary things," said London resident Ken O'Callaghan. "It must be comforting to people in Boston to know that people in London are thinking of them."

Londoner Cathy Ellis had been "very nervous" turning out to watch Margaret Thatcher's funeral procession earlier in the week. Then authorities identified two U.S. residents as the Boston suspects, "and that makes me feel less nervous about being here," she said. "We were relieved it wasn't an international thing. ... It's their deal."

Two Americans, on the other hand, said they weren't nervous at all, though they'd once lived in Boston and were devastated by the bombing.

"You can't live your life around it," said Giselle Schuetz of New York City, who was surprised by the relatively small crowds in London and by her ability to walk close to the finish chute.

About an hour before the start of the elite women's race, Amanda Trail, a government employee running her first marathon said that she was trying to put the events in Boston out of her mind.

"Runners are a tight community," she said, waiting in line at a local coffee shop on Blackheath's main street.

Lauren Kibble, who was waiting with her, and who is taking part in her third marathon, said that "in some ways we are more determined to have an even better race" than before.

By 9 a.m., thousands of spectators had already started congregating along the final stretch of the course, just in front of Buckingham Palace. Here in London,spectators are kept well away from the actual finish line on the city's famous "Mall," the broad avenue leading from the palace toward Trafalgar Square.

Buoyed by bright sunshine, spectators cheerfully applauded the junior wheelchair racers who were the first to head toward the finish. Helmeted bobbies and young army soldiers were almost as thick on the ground as spectators.

"I think it's sad that we have to have security like this when its just the marathon," said spectator Theresa Kalsky of London. "But it's good. You feel safe."

Race officials and the majority of runners wore black ribbons on their lapels or hats, but at the finish there was little sign that the Boston tragedy had raised anxieties.

"Anybody nervous?" David Bird of Saunderton, outside London, asked his teenaged daughters. They shook their heads. "Life goes on. ... You still have to think there's good in people."

On Saturday, Nick Bitel, London Marathon's chief executive, said: "In terms of our preparations, it's all gone well, obviously there were some additional security issues following Boston, but that seems to be bedding down and the message of reassurance to runners has been very well received."

Tower Bridge, Big Ben and the financial hub at Canary Wharf are some of the well-known landmarks that form the backdrop to the marathon's course, which is known for being relatively flat and fast.